The present invention relates to embossed cellulosic fibrous structures.
Cellulosic fibrous structures are a staple of everyday life. Cellulosic fibrous structures are used as consumer products for paper towels, toilet tissue, facial tissue, napkins and the like. The large demand for such paper products has created a demand for improved versions of the products and the methods of their manufacture.
Multiple ply cellulosic fibrous structures are very well known in the art of consumer products. Such products are cellulosic fibrous structures having more than one, typically two, plies superimposed in face-to-face relationship to form a laminate. It is known in the art to emboss sheets comprising multiple plies of tissue for aesthetic purposes and to maintain the plies in face-to-face relation during use. In addition, embossing can increase the surface area of the plies thereby enhancing their bulk and water holding capacity.
During the embossing process, the plies are fed through a nip formed between juxtaposed axially parallel rolls. Embossment knobs on these rolls compress like regions of each ply into engagement and contacting relationship with the opposing ply. The compressed regions of the plies produce an aesthetic pattern and provide a means for joining and maintaining the plies in face-to-face contacting relationship.
Embossing is typically performed by one of two processes, knob-to-knob embossing or nested embossing. Knob-to-knob embossing consists of axially parallel rolls juxtaposed to form a nip between the knobs on opposing rolls. Nested embossing consists of embossment knobs of one roll meshed between the embossment knobs of the other roll. Examples of knob-to-knob embossing and nested embossing are illustrated in the prior art by U.S. Pat. No. 3,414,459 issued Dec. 3, 1968 to Wells and commonly assigned; U.S. Pat. No. 3,547,723 issued Dec. 15, 1970 to Gresham; U.S. Pat. No. 3,556,907 issued Jan. 19, 1971 to Nystrand; U.S. Pat. No. 3,708,366 issued Jan. 2, 1973 to Donnelly; U.S. Pat. No. 3,738,905 issued Jun. 12, 1973 to Thomas; U.S. Pat. No. 3,867,225 issued Feb. 18, 1975 to Nystrand and U.S. Pat. No. 4,483,728 issued Nov. 20, 1984 to Bauernfeind.
Knob to knob embossing produces a cellulosic fibrous structure composed of pillowed regions which enhance the thickness of the product. However, the pillows have a tendency to collapse under pressure due to lack of support. Consequently, the thickness benefit is typically lost during the balance of the converting operation and subsequent packaging, diminishing the quilted appearance sought by embossing.
Nested embossing has proven to be the preferred process for producing products exhibiting a softer more quilted appearance that is maintained throughout the balance of the converting process including packaging. With nested embossing, one ply has a male pattern, while the other ply has a female pattern. As the two plies travel through the nip of the embossment rolls, the patterns are meshed together. Nested embossing aligns the knob crests on the male embossment roll with the low areas on the female embossment roll. As a result, the embossed sites produced on one ply provide support for the embossed sites on the other ply.
The lamination point at the nip between nested embossment rolls is typically eliminated, since the knobs on the nested embossment rolls do not touch. This necessitates the addition of a marrying roll to apply pressure for lamination. Typical marrying rolls are solid resulting in the lamination of every potential laminating point as shown in U.S. Pat. No. 3,867,225 issued Feb. 18, 1975 to Nystrand.
The nested embossment rolls may be designed such that the knobs on one roll contact the periphery of the other embossing roll providing a lamination point, thereby eliminating the need for a marrying roll. Such nested embossing arrangement is shown in U.S. Pat. No. 5,468,323 issued Nov. 21, 1995 to McNeil the disclosure of which is incorporated herein by reference. This arrangement also provides a means for improving the bond strength between the plies by enabling a glue applicator roll to be used in conjunction with each of the embossment rolls providing an adhesive joint at each of the embossed sites. Other ways of improving the bond strength between the plies are illustrated in commonly assigned U.S. Pat. No.: 5,858,554 issued to Neal et al. on Jan. 12, 1999 and U.S. Pat. No. 5,693,406 issued to Wegele et al. on Dec. 2, 1997, the disclosures of which are incorporated herein by reference.
Consumer testing of products having embossed cellulosic fibrous structures have determined that a softer, more quilted appearance is desired. Consumers desire products having relatively high caliper with aesthetically pleasing decorative patterns exhibiting a high quality cloth-like appearance. Such attributes must be provided without sacrificing the products"" other desired functional qualities of softness, absorbency, drape (flexibility/limpness) and bond strength between the plies.
The prior art teaches that embossing improves appearance and generally improves (i.e.; increases) the functional attributes of absorbency, compressibility, and bulk of the paper product while negatively impacting the drape (i.e.; increasing the bending stiffness) of the paper. The prior art also teaches that lamination improves appearance and generally improves bulk while negatively impacting drape (i.e.; increasing the bending stiffness of the paper).
This is illustrated in commonly assigned U.S. Pat. No. 5,693,406 issued to Wegele et al. on Dec. 2, 1997; U.S. Pat. No. 5,972,466 issued to Trokhan on Oct. 26, 1999; U.S. Pat. No. 6,030,690 issued to McNeil et al. on Feb. 29, 2000; and U.S. Pat. No. 6,086,715 issued to McNeil on Jul. 11, 2000, the disclosures of which are incorporated herein by reference.
Striking a balance between embossing/laminating used to create an aesthetically pleasing product and the functional attributes has always been difficult. The present invention provides a model known as the E factor for optimizing this relationship.
The present invention also yields unexpected results. Based on the prior art, one would expect the aesthetic appearance of the paper to improve as a function of embossing and laminating (i.e.; as embossing and/or laminating is increased the aesthetic appearance improves). Conversely, one would expect as less area of the paper is embossed and/or laminated, one would expect the aesthetic appearance of the paper to decrease.
Hence, it is very surprising to find that the present invention unexpectedly provides an aesthetically pleasing tissue and improvements in absorbency while utilizing less total embossed and laminated area, and while concurrently providing improvements in softness when compared to the prior art.
Softness is the pleasing tactile sensation customers perceive when they crumple the paper in their hands and while using the paper for its intended purposes. Softness is a function of the compressibility of the paper, the flexibility of the paper and the surface texture.
Absorbency is the characteristic of the paper which allows it to take up and retain fluids, particularlyxe2x80x94water and aqueous solutions and suspensions. In evaluating the absorbency of paper, not only is the absolute quantity of fluid a given amount of paper will hold significant, but the rate at which the paper will absorb the fluid is also important. In addition, when the paper is formed into a product such as a towel or wipe, the ability of the paper to cause a fluid to be taken up into the paper and thereby leave a dry wiped surface is also important.
The present invention relates to a model for describing an aesthetically pleasing tissue paper which also exhibits improved absorbency and softness utilizing less total embossed area as compared to the prior art. The embossed tissue paper of the invention may be comprised of one or more plies of tissue paper. The tissue paper includes a plurality of embossments. The paper has a total embossed area of about 15% or less and an E factor of between about 0.0100 to 3 inches4 per number of embossments (i.e.; about 0.416 to 125 cm4 per number of embossments). Each embossment is made on a roll having knobs which protude from about 0.05 inches to 0.1 inches from the plane of the roll (i.e.; about 0.127 cm to 0.254 cm).
The embossed tissue paper may also be further comprised of a plurality of domes. The domes are formed during the papermaking process. There are approximately from about 10 to 1000 domes per square inch of the tissue paper (i.e.; about 1.55 to 155 domes per square centimeter of tissue paper). The embossed tissue paper of the present invention will have a ratio of the number of embossments per unit area to the number of domes per unit area of about 0.025 to 0.25 and preferably about 0.05 to 0.15.
The embossed tissue paper may be comprised of one or more plies. At least one of the plies is embossed. The ply may be embossed on one or both sides of the tissue paper.